Method of covering a wire having interstices therein



Q J. E. FLOOD 2,479,919

METHOD OF COVERING A WIRE HAVING -IN'JJERSTICES THEREIN Filed Nov. 2'7, 1945 INVENTOR vfames' E. FY000 BYWML'W ATTORNEYS Patented Aug. 23, 1949 METHOD OF COVERING A WIRE HAVING r IN'IERSTICES THEREIN'. 1'.

James E. Flood, Norwich, Conn 'asslgnor to The *Plastic Wire &' Cable Corporation," Norwich,

Conn., a corporation of Connecticut Application November 27, 1945, seat No. 631,116

The present invention relates to method of making a covered wire and particularly to the securing of an extruded covering of thermoplastic resinous synthetic polymers such as polyvinyl chloride, copolymers of polyvinyl chloride such as copolymers of vinyl chloride-vinyl acetate, polyethylene, nylon and the like, to the wire.

I have found thatin extruding such covering material about a wire that the cover, While closely embracing the wire, retains its tubular form and does not satisfactorily bond or adhere to the wire as do vulcanizable compounds such as rubber or the like and that it slides on the wire when the wire is anchored and a pull is given to the covering. This has been true even when thewire is covered with a cotton wrap or'when' stranded wire has been used.

The present invention overcomes these difiiculties by providing a" mechanical interlock between the cover and the wire which is substantial and will hold the insulation against longitudinal displacement on the wire.

The mechanical interlock has been accomplished by rendering fluid a quantity of the cover material and applying a relatively'thin coating thereof to the wire so that it penetrates the interstices of the wire orcovering thereabout. 7 When this coating hardens, it will be mechanically'interlocked with the wire or wrapping and be secured thereto. The required quantity of cover material is then extruded over the thin coating on the wire and the two become integrally united into a single cover which is mechanically interlocked with the wire.

The cover material may be rendered fluid in many Ways. In one form of the invention the cover material is mixed with a solvent therefor which is driven off after the material is applied to the wire leaving the solid interlocked coating onthewire. I I

According to another form of the invention, the unplasticized cover material is dispersed'in a compatible liquid plasticizer in a suitable mixture under controlled conditions; The material'is one in which the mixing cycle is not quite'complete so that it remains as a heavy liquid coating when applied to'the wire.-

According to the present invention the coating mechanically connected to 'the'wire completely loses its identityas a coating when the jacket'of 5 Claims. (oils-59f hot cover material is applied thereto and merges Withand forms an integralpart thereof.

"The present invention is of particular advantagein connection with securing extruded thermoplastic resinous synthetic polymers as insulation on electrical conductors to "provide the necessary interlock to enable the cords made therefrom towithstand the pulls thereon in use.

v While it is preferred to use thecover material in' making the coating composition, it is to be understood that other compatible materials may be used. L} L 2 K Other advantages will be apparent from the specification and claims? when? considered with th'dra'wings in'which': i

Figural is'a side elevation of a wire having a coating thereon'l' QFig'. 2 is a section taken along line 22 of Fig. 1.

Fig'. 3 isa"sidefelevationbifa wire having a cover thereon; i

V Fig. 4 is a section taken along line 4--4 of Fig. 3.

Fig. 5 is a view showing awrapped wire.

Fig. 6 is 'a section taken along line 6+6 of Fig. 5.

The present inventionwill be described in connection with theapplication of a covering of in sula'tion'to an electrical 'cfon'ductor. However, it isto be understood that'wiresother than conductors .mayibec'overed for various other purposes; .7

As shown in the drawings, a wire I0 has a coverin'gll extrudedthereover. When the cover material comprises a synthetic resinous polymer, such as polyvinyl chloride or copolymers thereof such ascopclymers"of'vinyl'chloride=vinyl'acetate, polyethylene, nylon andfthe like which are water repellent and have good insulating properties, it

has" been found thatthesematerials will'not bond with" the'wire'-'but"'form"a spaghetti-like mass around the wirewhichwill readily slip with respect tothe wire'i This is particularly true when the conductoris used in iacord' set'and the wire anchored to the"'a'ttaching -connector or plug. Under-these circumstances, when the wire is gripped'and pulledto remove the connector, as'is usually; the case; th'e'insulation slides'relative to the wire and produces abare portion which renders's'uch-cords unfit for use;

In"order--to'-'securely anchor the insulation to the wireaccording to the present invention a wire having interstices-therein is employed; At

aevae 19 present preferred this may be a twisted or braided stranded wire or a smooth wire Illa having a Wrap or braid of cotton l3 thereon which will provide interstices through which a mechanical interlock between the insulation and the wire may be achieved. The term wire shall be used to designate both stranded or wrapped wire, singly or in multiples thereof.

The interlock, according to the present invention, is accomplished by preparing a coating of the insulation material which is sufficiently fluid that it will penetrate the interstices of the wire and become mechanically interlocked and anchored thereto.

The coating may be formed by mixing some of the insulation material with a suitable solvent, for example when vinyl chloride or the copolymer of vinyl chloride-vinyl acetate are used, acetone, methyl ethyl ketone, cyclohexanone or mixtures thereof may be mixed therewith to render the same liquid. The viscosity of the liquid maybe adjusted as required for the particular need. The wire in is run through a batch of the coating material which penetrates the interstices and applies a thin coating over the wire. The solvent is then allowed to evaporate or is driven off by means of heat or the like, leaving behind a very thin coating l2 of the compound mechanically anchored to the conductor or wrap thereabout as shown in Figs. 1 and 2.

The coated wire may pass through an oven or other heating means and the outer surfaces softened before it is fed to the cover or jacket extruding machine. However, I have found that with most compositions, when the coated wire is passed through the extruding machine and the cover or jacket of hot insulating material extruded directly on the coating, the heat of the cover material will be suflicient to melt the surface of the coating and cause it to become integral with the extruded insulation. As shown in Fig. 4 the coating and jacket of insulation form a unified cover of insulation which is anchored in the interstices in the wire and which will hold the insulation against slipping on the wire.

It is'preferable that the coating be thermoplastic at a somewhat lower temperature than the cover material so that it will readily melt and blend in with the jacket of cOVer material as it is extruded thereover. The heat of the jacket while suflicient to plasticize or soften the outer portion of the coating does not affect the portion of the coating which extends into the interstices and locks the coating to the wire so that when the insulating cover hardens it is securely mechanically connected to the wire.

Polyethylene and a suitable solvent therefor may be employed in a similar manner to provide a coating and the extruded cover.

The coating may also be formed by a quantity of the unplasticized resin such as polyvinyl chloride or copolymer of vinyl chloride-vinyl acetate,v

which is dispersed in a compatible liquid plasticizer in a suitable mixer and under controlled conditions. Such plasticizers may be dibutyl phthalate, dioctyl phthalate or others. The resin is ground in the plasticizer until a smooth uniform constant dispersion is formed. The mixture is a heavy liquid composition in which the mixing cycle is not complete, i. e. there is not a complete fluxing of the plasticizer and the resin.

The wire is run through a bath of the coating composition and the material is applied to the wire and penetrates into the interstices. The excess is wiped ofi. The bath is located behind the extruder so that the wire then passes into the extruder where the hot jacket of insulation or cover material is extruded thereover. The heat of the jacket causes the coating to change phase, 1. e., to complete the fluxing and change from a heavy liquid to an elastic solid and the jacket being of a similar composition and in a hot plastic state becomes fused with the coating into a solid mass which has portions interlocked with the conductor.

The coating materials and the cover may, of course, have suitable oils, pigments, stabilizers included in the mixture as required by the particular purpose for which the wire is to be used.

While I prefer to use the same material in the coating as in the cover, it is to be understood that other compatible materials which will fuse together to form an integral cover may be used.

Variations and modifications may be made Within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. A method of covering a wire comprising coating a wire having interstices therein with an unheated fluid coating composition of thermoplastic resinous synthetic polymer to cause the composition to enter said interstices and interlock therewith, and extruding a plastic jacket of cover material of the same thermoplastic resinous synthetic polymer in hot plastic form over the coating, the cover material and coating becoming an integral cover mechanically secured to the wire.

2. A method of covering a wire comprising coating a wire having interstices therein with an unheated fluid coating of cover composition to cause the composition to enter said interstices and interlock therewith, and extruding a jacket, of the same cover material in hot plastic form. over the coating, the hot cover material causing the coating to become fused therewith into an integral cover.

3. A method of insulating a conductor comprising mixing a thermoplastic resinous synthetic polymer with a solvent to form a fluid coating composition, coating a wire having interstices therein with said composition to cause the composition to enter said interstices; driving off the.

solvent to leave a thin coat of coating material on the Wire and interlocked therewith; and extruding a jacket of cover material of the same polymer in hot plastic form over the coating, the hot cover material causing the surface of the coating to become soft and fuse therewith into an integral cover.

4. A method of insulating a conductor comprising mixing a thermoplastic resinous synthetic polymer cover material with a solvent to form a fluid coating composition, coating 2, wire having interstices therein with said composition to cause the composition to enter said interstices; driving ofi the solvent to leave a thin coat of coating ma having interstices therein with said composition to cause the composition to enter said interstioes; and extruding a jacket of cover material of a compatible polymer capable of uniting by fusion with said synthetic polymer in hot plastic form over the coating, the hot cover material causing the coating to complete the fiuxing of the plasticizer and polymer and change phase from a heavy liquid to an elastic solid and fuse with the cover material into an integral cover.

JAMES E. FLOOD.

REFERENCES CITED The following references are of record in the file of this patent:

Number m Number 6 UNITED STATES PATENTS Name Date Koch July 15, 1941 Balthis et a1. Jan. 19, 1943 Brown Feb. 23, 1943 Smith Oct. 26, 1943 Williams Sept. 4, 1945 FOREIGN PATENTS Country Date Great Britain Dec. 2, 1922 

